Task 9: Speech perception

Question 1

Production of acoustic signal

Answer 1

Respiration (lungs) = air is pushed up from longs into vocal tract

Phonation (vocal cords) = vibration of vocal cords

Articulation (vocal tract) = moving articulators like tongue, lips, jaw, teeth and soft palate

Question 2

Two types of phonemes

Answer 2

Vowels (Fonants) and Consonants

Question 3

Vowels

Answer 3

• produced by vibration in vocal cords
• each sound = changing shape of vocal tract => changing resonant frequency
  => fonants are produced ( F1 and F2)

Question 4

Fonants are

Answer 4

peaks of pressure at different frequencies, associated with vowels

Question 5

Consonants

Answer 5

• produced by the closing of vocal tracts
• movement of articulators create patterns of energy
• rapid shifts in frequency occur before or after fonants, producing formant transitions, associated with vowels

Question 6

There are more vowels than standard set because

Answer 6

some of them have more than one pronunciation

Question 7

The acoustic signal from a particular phoneme is

Answer 7

variable

Question 8

Variability of acoustic signal

Answer 8

• coarticulation
• perceptual constancy
• speaker characteristics
• phonemic restoration effect

Question 9

Coarticulation

Answer 9

overlap between articulation of neighbouring phonemes (pronunciation of /n/ is influenced by the following phoneme)

Question 10

Perceptual constancy

Answer 10

• perceiving the sound of phoneme as being the same although the acoustic signal is changed by coarticulation
• included categorical perception, spectral contrast
  (McGurk and Yanny vs Laurel effect)

Question 11

Categorical perception

Answer 11

• stimuli that exist along continuum are perceived as divided into discrete categories
• voice onset time = time delay between when sound begins and vocal cords begin vibrating (/da/ has short VOT)
• phonetic boundary - curve or time from one phoneme to another

Question 12

McGurk Effect

Answer 12

• explains audiovisual speech perception = visual information influences what we hear
• listener hears /ba/ => lip movements of /ga/ => begins hearing /da/
• link between face and speech perception
  listening = superior temporal sulcus
  listening a familiar voice = STS + FFA

Question 13

Yanny vs Laurel Effect

Answer 13

• some people show preference for higher frequencies (hearing Yanny)
• other people show preference for lower frequencies (hearing Laurel)

Question 14

Speaker characteristics

Answer 14

individual differences and sloppy pronunciation

Question 15

Phonemic restoration effect

Answer 15

• sounds missing from speech can be restored in the brain and appear to be heard via:
• bottom-up processing = nature of the signal (similar frequencies between the missing and hear phoneme)
• top-down processing = context and expectations (long words)

Question 16

The process of perceiving words in sentences is influenced by

Answer 16

• knowledge
• speech segmentation
• transitional probabilities and statistical learning
• indexical characteristics of the speaker

Question 17

Cortical locations of speech perception

Answer 17

• Broca’s area
• Wernicke’s area
• Voice area

Question 18

Broca’s aphasia

Answer 18

• inferior frontal cortex
• difficulty producing speech (speaking)
• capable of comprehending

Question 19

Wernicke’s aphasia

Answer 19

• posterior temporal lobe
• difficulty comprehending speech
• speaks but not in a meaningful way (disorganised speech)
• word deafness = extreme case of aphasia when people cannot recognise words even if they are able to hear

Question 20

Voice area

Answer 20

• superior temporal sulcus
• activates to human voices
• contains voice cells

Question 21

Dual-stream model of speech perception

Answer 21

ventral (what) and dorsal (where) streams

Question 22

Ventral stream

Answer 22

• what? => recognising speech and meaning

- temporal lobe

Question 23

Dorsal stream

Answer 23

• where?
• linking acoustic signals to articulation
• parietal lobe + motor cortex